Two new receivers soon to be tested from the International Space Station could help fill holes in the current system used to keep tabs on ships traveling across the world's oceans.

In addition to helping ships avoid collisions and enabling authorities to track vessels, the enhanced detection system may help deter ship hijackings.

"Clearly the possibility to monitor the correct route of ships in the open seas can be a big advantage for discouraging pirate attacks," said the experiment's project manager, Giovanni Garofalo.

VHF radio signals transmitted by a ship's transponders are currently limited in horizontal range to about 40 miles. That leaves a vessel's identification and navigation data available only when it is along a coastline or when it is within range of another ship.

Yet signals from the Automatic Identification System — which are required on international vessels bigger than 300 metric tons, cargo ships more than 500 metric tons and all passenger vessels — travel much farther vertically, all the way to space, where theoretically they could be picked up by satellites.

The problem has been separating one AIS signal from another since, from orbit, the signals' shared frequencies collide with one another.

Early this year, scientists will begin testing two receivers aboard the space station, with the goal of developing instruments to track ships via satellite.

"In principle, any boat, of any nationality, with a standard transmitter could be detected in any sea accessible from (the space station's) orbit," Martin Zell, head of the International Space Station Utilization Department for the European Space Agency, told Discovery News.

"What we try to test is the capability to discriminate in waters populated by many ships which signals are simultaneously collected by the receivers," Zell said.

The receivers can be programmed to enhance AIS signal detection, discriminate between signals and reduce false hits.

During NASA's last shuttle mission in November, spacewalking astronauts installed a specially made VHF antenna to the outer hull of Europe's Columbus module. The two prototype receivers are already aboard the station, and a refurbished computer needed to route data is scheduled to be delivered to the outpost in March.

The experiment will begin shortly thereafter and run for at least a year.